Green and Blue Water

Holger Hoff1,2, Dieter Gerten1 , Jens Heinke1

1:Potsdam Institute for Climate Impact Research

2: Stockholm Environment Institute & Resilience Centre

a model & data based analysis of

water scarcity, productivity (and trade)

with a focus on the CPWF basins

data model

The LPJmL eco-hydrological & crop model

Photosynthesis

Carbon /

Water Balance

CO2 Temperature Precipitation Radiation

consistent simulation of water resources, plant water use and productivity

e.g. crop

production,

biofuels, carbon

sequestration

Crop yields

Surface flow

Interception

Transpiration

Subsurface flow

Water resources

Evaporation

.

biophysical processes at plant level

consistent calculation of green & blue virtual water contents (crops and other ecosystem services) AND water availability

Irrigation….. figure von Stefanie

surface runoff

demand

subsurface runoff

irrigation interception

transpiration

evaporation

plant water supply

precipitation

The LPJmL eco-hydrological & crop model

conveyance losses industry

withdrawals

return flows

livestock

household

lakes reservoirs

evaporation

landscape level

partitioning into green & blue

The LPJmL eco-hydrological & crop model reservoirs

Biemans et al 2011

current blue water availability per capita

m3 cap-1 yr-1

adding green water (evapotranspiration from cropland)

current green & blue water availability per capita

m3 cap-1 yr-1

potential for expanding cropland ?

discussion: country-wise aggregation of water for food

kcal m-3

current crop water productivity (kcal m-3)

water productivity -> weighted water availability

Sri Lanka 2129 kcal m-3

India 1648 Bangladesh 2697 Pakistan 1218

agricultural water productivity

kcal cap-1 day-1

maximum calorie production (kcal cap-1)

for current water availability & productivity

.

current green & blue water availability per capita

CPWF basins

Ganges Indus Limpopo Mekong Niger Nile Sao Francisco Volta Yellow

0

1000

2000

3000

4000

5000

6000

Ganges Indus Limpopo Mekong Niger Nile Sao

Francisco

Volta Yellow

blue water

green water

m3 c

ap

-1 y

ear-

1

0

500

1000

1500

2000

2500

Ganges Indus Limpopo Mekong Niger Nile Sao

Francisco

Volta Yellow

kc

al m

-3

.

factor 4

discussion: potential for closing the yield gap ?

.

current crop water productivity (kcal m-3)

CPWF basins

3000 a tipping point?

0

2000

4000

6000

8000

10000

12000

Gan

ges

Indus

Limpopo

Mek

ong

Nig

erNile

Sao

Fra

ncisco

Volta

Yel

low

kc

al c

ap

-1 d

ay

-1

.

maximum crop production (kcal cap-1)

for current water availability & productivity

CPWF basins

30 year averages

3000

3000 a tipping point?

inter-annual variability of green & blue water availability

.

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Ganges Indus Limpopo Mekong Niger Nile Sao

Francisco

Volta Yellow

CP blue

LPJ blue

CP green

LPJ green

CPWF basins

LPJmL vs CPWF data (1951-2000)

Co

V

using 10th percentile instead of mean green & blue water availability . .

factoring in variability

CPWF basins

3000 a tipping point?

0

2000

4000

6000

8000

10000

12000

14000

Gan

ges

Indus

Limpopo

Mek

ong

Nig

erNile

Sao

Fra

ncisco

Volta

Yel

low

kcal cap

-1 d

ay-1

3000

.

0

2000

4000

6000

8000

10000

12000

14000

Gan

ges

Indus

Limpopo

Mek

ong

Nig

erNile

Sao

Fra

ncisco

Volta

Yel

low

3000

kc

al c

ap

-1 d

ay

-1

the future (2050)

CPWF basins

discussion: 1) future crop water productivity (incl. CO2 effect)?

. 2) how much of the additional pressure is due to climate change?

0

0,5

1

1,5

2

2,5

3

3,5

1990 2000 2010 2020 2030 2040 2050 2060

Ganges

Indus

Limpopo

Mekong

Niger

Nile

Sao Francisco

Volta

Yellow

future water demand

population change only – relative to year 2000

discussion: future populations and diets ?

.

0

0,2

0,4

0,6

0,8

1

1,2

1990 2000 2010 2020 2030 2040 2050 2060

Ganges

Indus

Limpopo

Mekong

Niger

Nile

Sao Francisco

Volta

Yellow

climate change only – relative to year 2000

– 30 year averages, not accounting for changing variability, monsoon etc .

future (blue) water availability

.

.

next steps: simulating impacts of variability,

e.g. monsoon changes

Bondeau pers comm

.

next steps: simulating land use change effects

via “moisture recycling”

Indus „precipitationshed“

Nikoli et al

.

Sao F

rancis

co

Volta 

Nig

er

Nile

Lim

popo

Indus

Ganges

Mekong

Yellow

internal

0

10

20

30

40

50

60

70

80

internal

terrestrial

internally generated precipitation

basin precipitation originating from terrestrial ET

Nikoli et al

%

.

next steps: simulating land use change effects

via “moisture recycling” (external driver)

LPJmL simulations of ET changes with land use change

.

%

.

next steps: (“real”) water footprints

of food production (and trade)

plus other ecosystem services

e.g. carbon sequestration

.

Cyprus

LPJ-based crop virtual water contents

plus ComTrade data

-> virtual water im- / exports

consistent with water availability (“footprints”)

.

Sri Lanka 100m3 cap-1 net import India 5m3 cap-1 net export Bangladesh 30 m3 cap-1 net import Pakistan 2 m3 cap-1 net export

discussion: what happens under increasing future water scarcity?

see MENA example

0

200

400

600

800

1000

1200

0 500 1000 1500 2000 2500 3000 3500

water-limited potential kcal production per capita & day

VW

im

po

rts

(m

**3

) p

er c

ap

ita

&

ye

ar

Cyprus

LPJ-based crop virtual water contents

plus ComTrade data

-> virtual water im- / exports

consistent with water availability (“footprints”)

correlations of per capita

net VW imports and

- blue water availability: - 0.51

- blue plus green water avail: - 0.64

- water-limited potential

kcal production: - 0.79 - 0.79

.

1) Effects of international trade on local water resources

a) in water scarce (MENA) countries

.

m3 c

ap

-1 y

r-1